LivePlotter/main.cpp

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <vector>
#include <stdio.h>
#include <optional>

using namespace std;

const char* vertexShaderSource = "#version 330 core\n"
    "layout (location = 0) in vec3 aPos;\n"
    "void main()\n"
    "{\n"
    "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
    "}\0";

const char* fragmentShaderSource = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "void main()\n"
    "{\n"
    "   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);"
    "} ";

static GLFWwindow* window;

template<class T>
struct SimpleArray {
    T* data;
    size_t size;
};

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

void processInput(GLFWwindow* window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

bool glfw_window_setup() {
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    window = glfwCreateWindow(800, 800, "LearnOpenGL", NULL, NULL);
    if (window == NULL) {
        std::cout << "Failed to create GLFW windoww" << std::endl;
        glfwTerminate();
        return false;
    }
    glfwMakeContextCurrent(window);
    return true;
}

enum class ParserState {
    PREFIX,
    VERTEX,
    FACE,
    FACE_SKIP,
};
optional<pair<SimpleArray<float>, SimpleArray<unsigned int>>> load_iconsphere() {
    std::FILE* f = NULL;
    
    if (fopen_s(&f, "Iconsphere.obj", "r")) {
        return {};
    }

    // MEMORY LEAK!!! 84 verts currently
    float* vert_data = (float*)malloc(sizeof(float) * 128);
    size_t vert_data_size = 0;

    // MEMORY LEAK!!! (I think)
    unsigned int* indices_data = (unsigned int*)malloc(sizeof(int) * 256);
    size_t indices_data_size = 0;

    ParserState state = ParserState::PREFIX; 

    char ln[128];
    int len = 0;
    int start = 0;
    while ((ln[len] = std::fgetc(f)) != EOF) {
        switch (state) {
        case ParserState::PREFIX:
            if (len > 0 && ln[len - 1] == 'v' && ln[len] == ' ') {
                state = ParserState::VERTEX;
                start = len + 1;
            }
            else if (len > 0 && ln[len - 1] == 'f' && ln[len] == ' ') {
                state = ParserState::FACE;
                start = len + 1;

            }
            break;
        case ParserState::VERTEX:
            if (ln[len] == ' ' || ln[len] == '\n') {
                vert_data[vert_data_size] = atof(&ln[start]);
                vert_data_size++;
                start = len + 1;
            }
        case ParserState::FACE:
            if (ln[len] == '/') {
                state = ParserState::FACE_SKIP;
                indices_data[indices_data_size] = atoi(&ln[start]) - 1;
                indices_data_size++;
            }
            break;
        case ParserState::FACE_SKIP:
            if (ln[len] == ' ') {
                state = ParserState::FACE;
                start = len + 1;
            }
        }

        if (ln[len] == '\n') {
            len = 0;
            state = ParserState::PREFIX;
        }
        len++;
    }

    SimpleArray<float> verts = { vert_data, vert_data_size };
    SimpleArray<unsigned int> indices = { indices_data, indices_data_size };

    return make_pair(verts, indices);
}

int main()
{
    if (!glfw_window_setup()) return -1;

    auto data = load_iconsphere();
    if (!data) {
        std::cout << "ERROR loading the iconosphere obj file failed" << std::endl;
        return -1;
    }
    
    auto verts = data.value().first;
    auto indices = data.value().second;

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }
    glViewport(0, 0, 800, 800);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT); // Write to back buffer

    glfwSwapBuffers(window); // front buffer is now back
    glClear(GL_COLOR_BUFFER_BIT); // Write to back buffer again (former front buf)

    /*float vertices[] = {
    -0.5f, -0.5f, 0.0f,
     0.5f, -0.5f, 0.0f,
     0.0f,  0.5f, 0.0f
    };*/

    unsigned int VAO;
    glGenVertexArrays(1, &VAO);
    glBindVertexArray(VAO);

    unsigned int VBO;
    glGenBuffers(1, &VBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, verts.size * sizeof(float), verts.data, GL_STATIC_DRAW);

    unsigned int EBO;
    glGenBuffers(1, &EBO);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size * sizeof(unsigned int), indices.data, GL_STATIC_DRAW);
    
    // Vertex shader
    unsigned int vertexShader;
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);
    
    // Verify vertex shader compilation
    int  success;
    char infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success); 
    if (!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    // Fragment shader
    unsigned int fragmentShader;
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    // Verify fragment shader compilation
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    // Link shader programs together
    unsigned int shaderProgram;
    shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }
    glUseProgram(shaderProgram); // Set shaderProgram as active shader

    // Delete shader program parts (like deleting obj files). 
    // We want this memory back
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    // Tell opengl which attribute our data is for (i.e. location)
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

    while (!glfwWindowShouldClose(window))
    {
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawElements(GL_TRIANGLES, indices.size, GL_UNSIGNED_INT, 0);
        glBindVertexArray(VAO);

        processInput(window);
        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glfwTerminate();
    return 0;
}